Laminated core transformer



Oct. 20, 1970 E. b. BELANGER 3,535,665

LAMINATED CORE TRANSFORMER Filed April 14, 1969 United States Patent3,535,665 LAMINATED CORE TRANSFORMER Ernest Donald Belanger, Bloomsbury,N.J., assignor to Nytronics, Inc., Pelham Manor, N.Y., a corporation ofDelaware Filed Apr. 14, 1969, Ser. No. 815,845 Int. Cl. H01f 27/24 US.Cl. 336-178 Claims ABSTRACT OF THE DISCLOSURE This invention comprises alaminated core transformer FIELD OF INVENTION This invention relates toa laminated core transformer. More particularly this invention relatesto a transformer having a stacked core comprising sets of shapedlaminations which complete a magnetic circuit.

DESCRIPTION OF PRIOR ART Prior laminations in transformers have beenstamped in E-I, E-E, D-U, F, L, U-I shapes as well as in specialconfigurations for special applications. For transformer use, all aredesigned to be inserted into a previous wound coil. These coils may bewound on a bobbin or on a supporting tube with a material such as paperor other insulating material between the layers of wire for support ofthe winding. In some cases, wire with a bondable coating is used to makea self-supporting coil. In each case, the coil has to be wound withclearances so that the laminations can be inserted without damaging thecoil.

When miniature transformers are designed around these standard shapes,the clearances and/or bobbins occupy a much larger percentage of thewinding area available resulting in a very inefiicient transformer.

OBJECTS An object of this invention is to provide an eificienttransformer utilizing more effectively, available winding space.

A further object of this invention is to provide a core having sets oflaminations, each set comprising an H shaped and an I shaped element.

A still further object of this invention is to provide a laminated coretransformer having H and I shaped elements in which a coil is woundaround the cross-bar of the H element.

Yet another object of this invention is to provide a laminated coretransformer having H and I shaped elements occupying minimum space inwhich the ends of the elements are tapered providing easy insertion andproviding a complete magnetic core circuit.

A still further object of this invention is to provide H and I shapedelements stacked respectively together to provide a laminated core, inwhich the effective reactance is easily controlled and varied by themanner in which the elements are stacked.

Another object of this invention is to provide a method for assembling atransformer in which a winding may be placed directly around thecross-bar of an H shaped laminate to efficiently occupy the availableair space, and to complete the transformer with mating I shapedelements.

The above-mentioned and other features and objects ice of this inventionand the manner of attaining them will become more apparent and theinvention itself will be best understood by reference to the followingdescription of an embodiment of the invention taken in conjunction withthe accompaying drawing, wherein:

FIG. 1 is a perspective view of the laminated core transformer of myinvention;

FIG. 2 is a top view of an H shaped element used in the stackedlamination of FIG. 1;

FIG. 2A is a top view of the I shaped element;

FIG. 3 is a top view of another embodiment of the H shaped core piece;

FIG. 3A is a top view of the I shaped element used with the H of FIG. 3;

FIG. 4 is a diagram illustrating the position of the coil around the Hshaped core piece and the insertion of the I core piece; and

FIG. 5 is a diagram similar to FIG. 4 illustrating the removal of the Ishaped core piece.

Referring now to FIG. 1, there is shown a transformer 10 having alaminated core 20 and winding 11. One embodiment of the coreconstruction may be understood by referring to FIGS. 2 and 2A. In FIG. 2there is shown a core piece shown as generally H shaped having a rightleg 21, a left leg 14, and a cross-bar 28.

As an aspect of novelty in this invention, the H pieces may be stackedone above the other and the coil may be wound around the cross-bar toextend almost and very close to the outer extremity of the coil spacewhich is defined by the end or top surface of the right leg portion 23and the end surface of the lower left leg portion 25.

In providing the stackings, the H pieces are preferably alternatelyarranged so that the left leg 24 becomes the right leg in the nextsuccessive layer and vice versa. The left and right legs are preferablyeach of the dimension L. It will be noted that the staggering results inthe upper right leg portion 23 being shorter than the upper left legportion 26 while the lower right leg portion 22 is longer than the lowerleft leg portion 25. The differential in height resulting from thestaggering is an amount equal to W, which is the width of the I piece29, as will be understood later. In this way, a shape is provided ineach laminate or layer of which the I shaped element may fit into andyet be supported on its bottom surface by both the underlying I shapedelement as well as an extending portion of the respective leg. The coreis completed by the I shaped element 29, as illustrated.

Referring now to FIGS. 3 and 3A, there is shown my preferred embodiment.The H shaped piece 30 has a right leg 31, a left leg 34, and a cross-bar38. The legs are again staggered so that the outer lengths of the legsare the same as those of FIG. 2. As illustrated, the upper right leg 33and the lower left leg 35 are formed in the same manner as legs 23 and25 of FIG. 2. The lower right leg portion 32 and the upper left legportion 36 are cut to provide angled ends 41 and 42, respectively. The Ishaped element 39 of FIG. 3 is also cut to provide an angled end 40. Itwill be noted that I piece 39 has an upper surface (inner with respectto the entire core) of length L, but a lower (or outside) surface whichis greater. Because of the angular cut to the end, the said lowersurface has a length preferably equal to L+ W.

The manner of making the transformer will now be considered in greaterdetail. The H pieces are arranged in stack formation so that the leftvand right legs have respective layers preferably alternating. The Hlaminations are pre-assembled to the required stack height and heldtogether with suitable means such as with a thin piece of tape or withcement or by painting an adhesive on any or all of the exposed edges, orby using a thin heat shrinkable tubing over the cross-bar and/or thelegs and .then applying heat such as hot air for a few seconds. The hotair shrinks the tubing tight against the laminations. The assembledstack is then attached to the winding machine and the coil wounddirectly on the-lamination stack around the cross-bar of the H. Theadvantages are now obvious. No tube or margin clearances are required.

In miniature transformers, the working voltages are usually low enoughso that the normal insulation on the wire is enough protection. In somecases, it may be desirable to paint the winding area of the laminationstack with a thin insulating coat or wrap the legs with a thin piece oftape, or a piece of heat shrinkable tubing and shrinking it tight withthe application of heat.

After the coil is wound, the I pieces are inserted to complete themagnetic circuit. It should be noted that the H stack can be arranged inany of several different ways, depending on the magnetic propertiesdesired; they can be stacked alternately so that all joints are covered(used when maximum permeability is required) or they can be stacked allin the same direction and an air gap introduced between the H stack andthe I stack if desired (used in DC bias current applications, such asreactors or transformers with DC current in one or more windings). Theycan also be stacked in alternate sets of 2 or 3 or 4 etc. to achievewhatever magnetic properties desired.

The manner by which the end I pieces 39 are inserted and removed areillustrated ni FIGS. 4 and 5, the arrows suggesting insertion andremoval forces respectively. The alternate stacking of the H pieces isillustrated showing respective left and right legs of such H pieces arearranged on respective opposite right and left sides of the core. The Ipiece 39 is inserted and the left end thereof fits over the angled end41 of the next lower H piece. It will be noted that the angled end 40makes in and out adjustment possible without access to the coil spaceoccupied almost in total by coil 11. The angled end 40 mates with angledend 41 of leg 31 and provides complementary angular relationship.Typically, such angles may be 45 degrees. In this way the H and I piecescan lie flat in a plane. The angles formed are preferably complementary.If they are not exactly complementary, but so long as their total is 90degrees or less, the coil pieces may still lie flat and be coplanar,although some air space will appear in the space between the angledsurfaces.

In summary, there has been provided a laminated core transformer havinga stack of magnetic elements providing a laminated core in a transformerassembly, having H shaped and I shaped flat core pieces-and a coil woundaround and supported over the cross-bar of the H piece. The I pieces arepositioned to bridge the gap between the upper and lower ends of thelegs of the H. The width of the I piece is W, and the legs of the H arestaggered by an amount substantially equal to W, to provide a squarecore. The side dimension is L+ W. The legs of the H may be staggered,and the extending ends of the" legs maybe formed at an acute angle,along with the endof the I piece. The core pieces are arranged so thatthe said acute angles are additive, the acute angles in total being notmore than 90 degrees to allow the H and I pieces to lie flat. The H andI pieces may be optimally stacked to provide a core substantially devoidof air space between the core pieces or the ends of the H and I piecesmay overlap to provide a core having air spaces between the respectivelaminates. The coil therefore substantially occupies the space between.the crossbar of the H and the inner side of the I piece.

While the foregoing description sets forth the principles of theinvention in connection with specific apparatus, it is to be understoodthat this description is made only by way of example and not as alimitation of the scope of the invention as set forth in the objectsthereof and in the accompanying claims.

What is claimed is:

1. A laminated core transformer comprising:

a stack of magnetic elements providing a laminated core in a transformerassembly;

said stack comprising sets of substantially H shaped and I shaped flatcore pieces;

a coil wound around and supported over the cross-bar of the H piece;

the I pieces being positioned to bridge the gap between the upper andlower ends of the legs of the H.

2. The core transformer of claim 1, in which the width of the I piece isW, and in which the legs of the H are staggered by an amountsubstantially equal to W, whereby a square core is provided having aside substantially equal to L+ W.

3. The core transformer of claim 1 in which legs of the H are staggered,and in which the extending ends of the legs are formed at an acuteangle, and in which at least one end of the I piece is formed at anacute angle.

4. The core transformer of claim 3, in which said core pieces arearranged so that the said acute angles are additive said acute angles intotal being not more than 90 degrees to allow the H and I pieces to lieflat.

5. The core transformer of claim 1 in which the extending leg ends ofthe legs of H are formed at an acute angle and in which the end of the Ipiece is formed at an acute angle.

6. The core transformer of claim in which the I pieces are arranged sothat the angles are additive,

said acute angles being, in total, not more than 90 degrees to allow theH and I pieces to lie flat.

7. The core transformer of claim 5 in which the ends of the H and Ipieces overlap whereby a core is provided having air spaces therein.

8. The core transformer of claim 5 in which the coil substantiallyoccupies the space between the cross-bar of the H and the inner side ofthe I piece.

9. The core transformer of claim 1 in which the H pieces are uniformlystacked with respect to left and right sides of the core.

50 10. The core transformer of claim 1 in which at least some of the Hpieces are alternately stacked with respective left and right legs ofsuch H pieces being arranged in respective opposite right and left sidesof the core.

References Cited US. Cl. X.R.

